Illuminated bubble level



March 14, 1944. a F. FLINT ILLUMNATBD BUBBLE LBVBL.l

Filed'Ja'n'. 28, 1942 may#v EDWARD E'FLINT INVENTOR n ATTORNEY Ww H@ slil. v

Patented Mar. 14, 1944 ILLUMINATED BUBBLE LEVEL Edward F. Flint,Rochester, N. Y., assigner to Bausch & Lomb Optical Company, Rochester,N. Y., a corporation of New York Application January 28, 1942, SerialNo. 428,583

7 Claims.

This invention relates to bubble levels and more particularly it hasreference to illuminated bubble levels such as are adapted for use insextants, octants and the like.

One of the objects of my invention is to provide improved means forilluminating a bubble level. Another object is to provide a bubble levelhaving simple yet efcient means for uniformly illuminating the bubblethereof. A further 'object is to provide a bubble level having efiicienmeans for providing dark-held illumination oi' the bubble. These andother objects and advantages reside in certain novel features ofconstruction, arrangement and combination of parts as will hereinafterbe more fully explained and Apointed out in the appended claims.

Fig. 4 is a plan View of the light transmitting member.

A preferred embodiment of my invention is disclosed in the drawingwherein lli indicates a housing having a central opening Il extendingtherethrough. An inwardly projecting boss I2 provides a seat againstwhich is held the upper transparent member I3 by means of a threadedlock ring lli and a gasket I 5 and a lower transparent member IS is heldagainst the boss I2 by the threaded lock ring Il and gasket I8. Thetransparent members may be formed of any suitable transparent materialsuch as glass or plastic and their surfaces may be plane or formed withany desired curvature. There is thus formed between the members I3 andl5 a chamber I9 which is adapted to contain a liquid 20, such as xylol,having therein a bubble 2i. The size of the bubble may be controlled byadjustable diaphragm means contained in housing 22, although the detailsof such means are not shown since they form no part of the presentinvention.

Illumination of the bubble 2i is provided by a layer of luminescentmaterial 23 which is applied as an annular border around the outerperipheral portion of the outer surface of member I6. The layer ofmaterial is applied directly to the surface of the member I5 so that itis in optical contact therewith. Although the layer 23 may, undercertain conditions, provide suicient illumination for the bubble 2|, itmay be desirable to apply an additional layer of luminescent material 24in optical contact with the outer surface of member I3. The layers ofmaterial 23 and 24 may comprise radium paint which is self-luminous orthey may comprise phosphorescent paint which emits light followingexcitation by a light source.

If the layers of material 23 and 24 comprise phosphorescent material, itis, of course, necessary to provide a source of light rays for.activating the phosphorescent material. On the other hand, if aself-luminous material, such as radium paint, is employed, it is notabsolutely essential to employ a light source for exciting the material.However, a material such as radium paint usually comprises aphosphorescent substance, such as zinc sulphide, and a radioactivesubstance which activates the phosphorescent substance. Hence, if it isdesired to increase the illumination produced by radium paint, it may beaccomplished by exposing the paint, :and its constituent phosphorescentsubstance, to light rays from another source.

In a preferred construction, therefore, the layers of material 23 and 24are made of radium paint which is preferably also activated by lightrays emanating from another source, such as an electric lamp 25 mountedin the housing i8. Mounted directly below the layer `2.3, and extendingsubstantially coextensively therewith, is the annular light transmittingmember 26 having a projection 21 which is frictionally held in a slot 28in housing It so as to support the member 26 in position so that lightrays from lamp 25 may enter the projection 2l and pass around the member26. The member 2t and the projection 21, which may be either integralwith or cemented onto the member 25, may be formed of any suitable lighttransmitting material such as quartz or a clear plastic material soldunder the trade-mark Lucite. Light rays from lamp 25 enter theprojection 21 and pass into the member 26 and then, by internalreflection, pass around the member 26. Due to irregularities on itssurface, the member 26 will glow so that light rays will emanate fromall sides thereof and so will activate the luminescent material in layer23. In order to prevent light rays from reaching the bubble 2I directlyfrom the lamp 25 and thereby causing uneven illumination, an opaque plug29, made of bre or the like, is positioned in the re-entrant portion 30formed in member 26 opposite the lamp 25.

Positioned beneath the transparent member i6 is a cylindrical member 3lhaving a ange 32 which is attached to the housing I0 by screws 33.

The cylinder 3| and flange 32 provide a housing for the lighttransmitting member 26 and since the cylinder is opaque no light rayscan pass directly from the member 26 to the eye of an observer who islooking through the level. Similarly, an annular opaque shield 34 havinga central aperture 35 is positioned above the layer 24 on the member I3to prevent light rays from the layers 23 and 24 from passing directly toan observers eye. It will be apparent, therefore, that light rays fromthe luminescent layers 23 and 24 will pass directly through thetransparent members I3 and I6 to illuminate the wall of the bubble 2lwhile some rays will be reflected by the surfaces of the members andonto the wall of the bubble. Since layer 23 is activated by the member26, some rays from layer 23 will also strike layer 24 and tend toactivate it also. In order to render the illumination more uniform, thewalls adjacent the three sides of member 26 are also coated with layersof luminescent material 3@ such as zinc sulphide or the like.

It will be apparent, therefore, that light rays will strike the wall ofthe bubble 2| and since no light rays reach the observers eye directlyfrom the illuminating means, the illuminated bubble 2| will appear as aluminous ring on a substantially dark background. Since the verticaldimension of chamber i9 is relatively small, the bubble 2| extends fromthe inner surface of one` transparent member to that of the other. Suclaa construction is advantageous in instruments such as sextants oroctants, since it permits an observer to look through the bubble withoutthe distortion which is present when a bubble is bounded on its underside by an amount of liquid. With my improved illumination system, sucha bubble appears as a sharply dened luminous ring on a dark backgroundas the wall portions of the bubble in contact with the surface of themember I3 will reflect a relatively large number of the light rays whilethe wall of the bubble in contact with the surface of the member I 6will refract much of the incident light into the eye of the observer.Since the layers of luminescent material 23 and 24 are in opticalcontact with the surfaces of members I3 and I6, the rays from the layerspass into the members without losses by reflection which would otherwiseoccur if the layers were not in optical contact with the transparentmembers.

From the foregoing, it will be apparent that I am able to attain theobjects of my invention and provide a bubble level having improved meansfor illuminating the bubble. Various modications can obviously be madewithout departing from the spirit of my invention.

I claim:

i. A bubble level comprising a housing, upper and lower transparentmembers horizontally mounted in said housing, said members beingvertically spaced apart to provide a bubble chamber therebetween, liquidin said chamber and a bubble in said liquid, said bubble extending fromone member to the other member, and means for illuminating said bubblecomprising a border of luminescent material positioned on the outer faceof one of said members and means for exciting said material, saidmaterial being in optical contact with the face of said member and thelight rays emitted therefrom angularly traversing said member beforestriking theA wall of said bubble.

2. A bubble level comprising a housing, upper and lower transparentmembers horizontally mounted in said housing, said members beingvertically spaced apart to provide a bubble chamber, liquid in thechamber and a bubble in the liquid, means for illuminating the bubblecomprising an annular layer of luminescent material positioned on eachouter face of said members and extending as borders around the edgesthereof, means for exciting said layers comprising annular lightconducting means positioned adjacent to and substantially coextensivewith the layer on one of the members and a light source adjacent saidlight conducting means for supplying light rays thereto, and shieldingmeans for preventing light rays from said layers and light conductingmeans from directly entering the eye of an observer looking through thelevel.

3. In a bubble level the combination of a housing, two vertically spacedmembers horizontally mounted in the housing to provide a chamber, liquidin the chamber and a bubble in the liquid, one of said members beingtransparent, and means for illuminating the bubble comprising an annularlight transmitting member positioned adjacent the outer face of thetransparent member and extending around the border thereof, a lightsource positioned to direct light rays into said light transmittingmember, and means for producing uniform illumination of the lighttransmitting member comprising layers of luminescent materialsubstantially surrounding the walls of the light transmitting member.

4. A bubble level comprising a housing, two transparent membershorizontally mounted in superposed relation in said housing to provide achamber therebetween, liquid in said chamber and a bubble in the liquid,said bubble being compressed between said members, means forilluminating the bubble comprising a layer of luminescent material inoptical contact with the outer face of one of the members, saidlayerextending as a border around the face or" the member with a free centralopening through which the bubble may be viewed, means for exciting saidmaterial comprising annular light transmitting means positioned adjacentto and substantially coextensive with said layer and a light sourceadjacent said light transmitting means for supplying light rays thereto,and an opaque light shield positioned adjacent the other of saidmembers, said shield having a central opening through which the bubblemay be viewed.

5. A bubble level comprising a housing, spaced upper and lowertransparent members spaced apart in said housing to provide a bubblechamber, liquid in said chamber and a bubble in the liquid, said bubbleextending from one member to the other whereby light rays may passthrough the members and the central portion of the bubble withouttraversing any substantial amount of the liquid, and means forilluminating the wall of the bubble comprising layers of luminescentmaterial positioned around the outer portions of the outer faces of saidmembers, means for activating said layers of material comprising ahousing positioned below and substantially coextensive with the layer onthe lower member and having its upper side open to the layer, the innersurfaces of the housing being coated with luminescent material, a lighttransmitting member in the housing and extending substantiallycoextensively therewith, and a light source adjacent the lighttransmitting member whereby light rays from said source Will excite theluminescent material.

6. A bubble level comprising a housing, two transparent membershorizontally mounted in superposed relation in said housing to provide achamber therebetween, transparent liquid in said chamber, a bubble inthe liquid, means for illuminating the bubble whereby to render itvisible as a luminous ring on a dark background, said means comprisingan annular layer of luminescent material positioned on and extendingaround the peripheral portions of the outersurface of each of saidmembers, said layers of material being in optical Contact with saidsurfaces, means for exciting said layers of material comprising anannular light transmitting member positioned adjacent to and extendingsubstantially coextensive with one of said layers of material, a lightsource for supplying light rays to said light transmitting member, andcentrally apertured shielding means for preventing light rays from thebubble illuminating means from directly reach- 20 ing the eye of anobserver looking through the level.

7. A bubble level comprising a housing, two horizontally disposedtransparent members carried by said housing, said members beingvertically spaced apart to provide a chamber therebetween, a liquid inthe chamber and a bubble in the liquid, annular layers of luminescentmaterial carried by and in optical contact with the marginal portion ofthe outer faces of the transparent members, an annular member of lightconducting material disposed adjacent one of said layers of luminescentmaterial with one face thereof closely spaced from said layer, means fordirecting light to said annular member, and layers of luminescentmaterial substantially surrounding the remaining faces of said lightconducting member.

EDWARD F. FLINT.

